The present invention is directed generally to reciprocating piston pumps and more particularly to valves used in reciprocating piston pumps.
Reciprocating piston pumps typically include an air-driven motor that converts a steady flow of compressed air into linear reciprocation of an air motor shaft using appropriate reversing valves and pilot valves, as are known in the art. The air motor shaft is then used to drive a linearly reciprocating piston that can be configured to pump in both directions using appropriate check valves.
These types of linearly reciprocating double-acting piston pumps are commonly used in lubrication dispensing systems to deliver highly viscous lubricants, such as oil. These pump systems are typically installed in commercial facilities arranged for high-volume dispensing operations. For example, large containers or drums are connected to the pump inlet, sometimes through the use of extension tubing. Likewise, the fluid dispensing device, such as a hand-operated nozzle, is connected to the pump via lengthy extension hoses so the nozzle can be brought to a specific location. It is undesirable due to convenience and waste factors to purge these systems after each use. However, lubricant remaining in the extension hoses can compromise the system if lubricant is not dispensed for a long period of time. In particular, thermal expansion of the lubricant due to temperature swings can cause the lubricant to increase in pressure to such a degree so as to rupture the extension hose or any other pressure containing component. For example, sometimes the container and pump can be stored outside of the facility for safety and convenience factors. Temperatures rises downstream from the pump system, such as in the dispenser and extension hose, can cause the oil to expand, which causes extreme rises is system pressure.
Conventional lubrication systems incorporate a pressure relief valve in the extension hose near the pump to permit thermally expanded lubricant to bleed from the system. Such a solution, however, requires the use of additional tubing and a container to capture the purged lubricant, which adds undesirable inconvenience, expense and complexity to the system. There is, therefore, a need for a simpler and less expensive venting mechanism.